1. Field of the Invention
The present invention relates to a transmission apparatus and, more particularly, relates to a transmission apparatus including an oil supplying mechanism for introducing oil into an intra-shaft oil passage in a rotating shaft from inside of a case, and then supplying the oil to fitting portions where gears and the like are fitted on an outer peripheral surface of the rotating shaft.
2. Description of the Related Art
Such a mechanism for supplying oil, for example, has been used for lubricating portions where speed-change gears are fitted on a speed-change shaft, in a gear transmission. As a system for supplying the oil into the rotating shaft from outside, there have been a forced-supply system utilizing an oil pump, and a natural-supply system utilizing water-head differential pressure (head differential pressure) in oil. The forced-supply system hardly induces shortage of the amount of supplied oil into the rotating shaft, except in an event of failures of the oil pump, and the like.
However, in the natural-supply system, it is necessary to transfer or lift the oil upwardly from a case to a certain height which will result in a water-head differential pressure in the oil. Japanese Examined Utility Model (Registration) Application Publication No. 61-12451 discloses a lubricating mechanism which supplies oil by utilizing a large-diameter ring gear 201, as illustrated in FIG. 11. The structure illustrated in FIG. 11 will be described briefly. An oil passage is formed in a space between outer teeth 201a of the ring gear 201 and an inside wall surface 202a of a transmission case 202. Oil in the transmission case 202 is transferred or lifted up through the oil passage by rotation of the ring gear 201, and supplied in an oil receiver 203 located in a height position. The oil receiver 203 is communicated with an intra-shaft oil passage 205 of a rotating shaft 204 which is positioned at a level lower than a level of the oil receiver 203.
With respect to the mechanism of FIG. 11, although the oil is transferred upwardly in the space between the outer teeth 201a and the inside wall surface 202a, some or most of the oil flows out laterally in an axial direction from the space along the way between a lower end portion of the ring gear 201 and an upper end portion thereof. Namely, losses of the transferred oil amount will become large, and oil transfer efficiency will become low.